[Raba]

Hello everyone. Im planning on staring to build a 5 x 10 CNC router. For the X and Y axis Im planning to use belts. What type of belts do you guys use (Xl, L HTD, etc.) and what width? Also does any one know a good supllier, I live in the Midwest.

Thanks in advance.

[harryn]

Hi, There is a lot of good information on belts on the brecoflex web site. The amount of information on belts and the application is just astounding. From there, you can make quite an informed decision.

I am also working (slowly) on a belt drive router, so if you search around on the threads I have posted in, there might be some useful information in that as well.

I was surprised at just how robust of belts are needed on a large router. The forces can be considerable.

[Raba]

Thanks harryn. I checked it out and I might order from them. What did you end up getting?
I also have one more question. Has anyone tried slaving servo motors, I would like to use two servos to drive mine X axis.

[harryn]

Hi, my project is still funds limited, so actual purchases have been slow, including the belt and pulleys.

My latest belt calculations, guesses and info are in this thread. I had been hoping more people would comment on them, but so far, not many takers.

http://www.cnczone.com/forums/mechan...ml?#post848610

So, far, I am leaning toward 150ATL10 (6 in wide, ATL 10 belt with steel wires). I originally used tooth strength to calculate, which indicated that 25mm wide belt would be fine, but then I was reminded about stretch, and that drove a wider belt selection. In the end, it all comes down to investment vs tolerances, regardless of the drive approach.

[Hyrum R]

I built the belt-drive solsylva table a while back (with several modifications, I might add.) Belts are wonderful for fast jog speeds and light cutting, but there's just too much stretch and bounce to do any heavy cutting at a very fast speed. I can jog at over 800ipm all day long, but I'm lucky to be able to cut 1/4" deep at 75 ipm.

If I had it to do over again (and I am going to be....once I get enough $$$ together ), I'd go with rack & pinion. The components are close to the same price, but it seems to me, you'd get a much more rigid machine.

[harryn]

I built the belt-drive solsylva table a while back (with several modifications, I might add.) Belts are wonderful for fast jog speeds and light cutting, but there's just too much stretch and bounce to do any heavy cutting at a very fast speed. I can jog at over 800ipm all day long, but I'm lucky to be able to cut 1/4" deep at 75 ipm.

If I had it to do over again (and I am going to be....once I get enough $$$ together ), I'd go with rack & pinion. The components are close to the same price, but it seems to me, you'd get a much more rigid machine.

Hi, thanks for that info. Could I ask what size and type of belts you used ? Most people seem to use 1/2 to 1 in wide belts, while my calculations indicate something more like 6 in wide is needed for serious work.

[Raba]

Hyrum R, 75 ipm does sound too slow for machine that size. What belt width did you use? And harryn, Brecoflex only has 100mm of that particular belt, where are you planning to get the belt 6in wide?

[harryn]

Hyrum R, 75 ipm does sound too slow for machine that size. What belt width did you use? And harryn, Brecoflex only has 100mm of that particular belt, where are you planning to get the belt 6in wide?

Figures. I was hoping to just use one belt for my Y axis 150 mm wide. I guess I need to either go to AT for 150mm, or 2 belts x 75 - 100 wide. I was really hoping to eliminate a pulley set by going to one wide belt.

[Hyrum R]

The belts on my machine are 1" (correction: 3/4") wide. If I was cutting foam, I'd let it rip at 500ipm. Anything with much force really causes trouble, though.

[Raba]

Hyrum R, I checked out your build thread and it looks like you have fixed belt design for X and moving belt for Y. Which of the axis causes more trouble?

[Raba]

harryn, I looked at your build thread and it appears you want to cut aluminum as well? Im building my router to cut mostly plywood and MDF. Also my gantry will not be moving up/down, so I guess my belts don't have to be that wide?

[Hyrum R]

If anything, the Y axis seems to have a little more trouble than the X. It's not too much of a problem as long as you know the limitations of the machine. I have a lot of ideas going through my head right now about a bigger better machine. (Don't we all. )

[Raba]

Oh yeah we all do (4th axis, glass cutting attachment). Im actually looking at the rack and pinion for the X. There is an Ebay seller selling rack and pinion at reasonable prices Rack 1500mm/59.05" 26T Pinion CNC Router Plasma Laser - eBay (item 150318787203 end time Nov-21-10 15:04:28 PST). Has anyone had any experience with them?

[harryn]

harryn, I looked at your build thread and it appears you want to cut aluminum as well? Im building my router to cut mostly plywood and MDF. Also my gantry will not be moving up/down, so I guess my belts don't have to be that wide?

Hi, over time I accepted that cutting Al is not that practical for my machine. I am setting up to be able to drill it though, which is a lot easier.

In that thread I pointed to, the forces are broken out by:
- forces from gravity
- forces from acceleration
- forces for holding things still to cut accurately

You can estimate from there.

As others have pointed out, it takes a very stout belt to not stretch, and that is where rack and pinion are interesting.

There are tons of threads on rack and pinion builds.

[ger21]

You should be able to get rack and pinion for much less than that. McMaster Carr has 20°PA 20 pitch for about $46 for 6 ft, and $17 for a pinion. Most are buying their racks from Moore Gear Website It's apparently better quality than McMaster Carr and possibly even cheaper.

Harry, I'd expect 6" wide belt to cost a fortune, or at least far more than any other conventional drive method.

[Raba]

Thanks everyone for the fast replies. After searching all over the zone i decided to go with the rack and pinion for the X axis. But I'm still trying to figure out the best way to eliminate backlash. As there any good DIY solutions?

[Raba]

Does anyone know what is the minimum Pinion tooth for 20°PA 20 pitch rack?

[Diane-MooreGear]

Minimum number of teeth on a stock pinion 20DP-20PA is 12T. Most people use something between 15T and 24T with 20 being the most common. I'd worry about the undercut, backlash, wearing on the 12T since that is tiny as spur gears go.

Diane
Moore Gear

[fatal-exception]

6" wide steel belt? Yeah, I would guess that it would cost more than nearly any other drive system. By the time you make all the idlers and other components, I doubt you would be ahead of the game, and the complexity would also go up.

We used belts for a 2'x4' plasma table and it works fine. Rapids of up to 1200ipm and possible, but I doubt I would even consider this type of drive system for a router or mill, there's just too many other tried and true methods available out there.

If there's very little force (like plasma cutting) and you need high speeds, then belt is the way to go. R&P or ballscrew for heavier applications.

Paul

[Raba]

Yeah, I decided to go with R&P. I ordered the pinion drive from CNCRouterParts.com, and rack from Moore Gear.
Has anyone used them successfully with servos?